- B The energies emitted during electron transitions are equal to the
differences between the allowed energy levels. Choice (A), 17 eV, is equal
to the energy emitted by the photon when an electron drops from the −21 eV
level to the −38 eV level. Choice (C), 64 eV, is equal to the energy emitted
by the photon when an electron drops from the −21 eV level to the −85 eV
level. Choice (D), 255 eV, is equal to the energy emitted by the photon when
an electron drops from the −85 eV level to the −340 eV level. And (E), 302
eV, is equal to the energy emitted by the photon when an electron drops from
the −38 eV level to the −340 eV level. However, no electron transition in
this atom could give rise to a 42 eV photon. - A Call the top wire (the one carrying a current I to the right) Wire 1, and call
the bottom wire (carrying a current 2I to the left) Wire 2. In the region
between the wires, the individual magnetic field vectors due to the wires are
both directed into the plane of the page (use the right-hand rule with your
right hand wrapped around the wire and your right thumb pointing in the
direction of the current), so they could not cancel in this region. Therefore,
the total magnetic field could not be zero at either Point 2 or Point 3. This
eliminates (B), (C), (D), and (E), so the answer must be (A). (Because the
magnetic field created by a current-carrying wire is proportional to the
current and inversely proportional to the distance from the wire, the facts that
Point 1 is in a region where the individual magnetic field vectors created by
the wires point in opposite directions and that Point 1 is twice as far from
Wire 2 as from Wire 1 imply that the total magnetic field there will be zero.) - C The proximity of the charged sphere will induce negative charge to move
to the side of the uncharged sphere closer to the charged sphere. Since the
induced negative charge is closer than the induced positive charge to the
charged sphere, there will be a net electrostatic attraction between the
spheres.
marvins-underground-k-12
(Marvins-Underground-K-12)
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